Safety-limit switch.



No. 881,565. PATENTED MAR. l0, 1908. H. A. EVERETT dz A. PARKER.

SAFETY LIMIT SWITCH.

APPLICATION FILED JULYZB, 1907.

HEY

`or motors or t y which will UNI/TED srrirns,

PATENT oiniroleit `HENRY A. EVERETT, OF BARRINGTON, NEW JERSEY, AND ARTHUR PARKER, 1 i v OF PHILADELPBA, PENNSYLVANIA. i

y SAFETY-LIMIT, SWITCH.

spcification of Letters Patent.

Patented Maren 1b, 1908.

4Be it known that we, HENRY A. EVERETT and 'ARTHUR PARKER, citizens of the United States, residing, respectively, at Barrington, in the county of Camden and the State of New Jersey, and of Philadelphia, in the county of Philadelphia 'and State of Pennsylvania, `have invented ,certain new and useful Im rovements in Safety-Limit Switches, of which the followingfis alspecification.

Our invention relates. to that class of switches that are used as protective devices fand our objects are to provide a means to prevent thejchain block on an electric hoist from assuming afjamming position to the structural work on said hoist, and thereby preventing the breaking of the chain' or wire rope, or causing injury to the electric motor e wiring connected thereto, and to eliminate all chances of` accidental loss of life due to any of the above causes.:

Reference is to be had to the accompanying drawin formin part hereof, and in e seen t e construction of our, apparatus, Whereim-v i *ign/re lshows a sectional elevation of f the a paratus mounted upon an appropriate ane or base. Fig. 2 shows a lan view, and ig. 3 shows a wiring diagram i lustrating the' Y vcircuits of either position of the switch. Fig.

4 is an elevation of an insulated to a screw shaft.

In the accompanyin drawing in which similar numerals of re erence indicate corresponding parts in the several views, the numeral 1 indicates the blade of a single pole pinion keyed double throw switch, 2 is the pivot point, 3

and 4 areswi-tch 'clips by which the switch blade 1 enga es ineither position..

5 is a s ira sprin surrounding the pivotal shaft 6 o the switc blade 1, o`ne end of said sprin being .fastened `to the switch blade and tV e other end to the b'ase upon which the switch is fmounted. This spring upon with the clip 4.

reacting causes the switch blade 1 to engage 7 is a spiral extension spring/which accomplishes the same result as spring 5; 22 is a suitable base upon which the apparatus is mounted.

8 is a pin rigidlyattached to the switch blade 1.

9 is a, dog' or finger pivoted at 1() and adapted to engage with the pin 8.:

13 is a screw actuated by the pinions 14 and 15.'

15 is one of the pinions in a' hoisting train of gears. The pinion 14 is insulated by the insulation 30 and keyed to the shaft by' the key 31.

11 is a carrier which engages with the screw 1.3. l

12 is a guide rodfwhichserves as a guide for the carrier11.

land 17 are end bearings for the screw 13 and the guide rod 12 and also upon which the base 22 is mountedkand made adjustable in a position relative to the carrier 11.I

18 is a .motor controlling the aforesaid train of gears for the hoistin apparatus.

19is the 'field winding for t e said motor.

2() is the hoisting'side of thel controller and 21 the lowering side. A

'23, 24, 25, 26, 27, 28 and 29 are leads connecting the controller, motor, motor field winding ,-and safety limit switch.v

The foregoing apparatus is suitably proportioned and mounted on an eappropriate panel, all of which will be readily understood by those skilled in the art to which this in vention relates. Its mode of operation will be substantially as follows: In mesh with or actuated by one of the gears orpinions'in a ltrain of gearing for an electric hoist, the insulated vpinion 14 is placed. The pinion 14 and the screw 13 are so proportioned that the extreme travel of the cham block will move the carrier 11 a somewhat less distance than that between the finger 9 and the end bearing 16.Y The switch blade being forced into engagement, against the springs 5 and 7, with clip 3 and held therein by the finger 9 engaging with the pin 8.v After the chain block has' assumed a predetermined `osition the carrier/11 is set so as any further iolstlng movement will cause the carrier 1 1 to engage with the finger 9. From Fig. 3 it will be seen that a lowering or' hoisting movement of the chain block can be accomplished, the circuits being substantially as follows; for hoisting, positive lead 29 by controller to lead 28, safety switch blade 1, lead 25 armature 18, lead 26, by controller to lead 27, field winding 19 and lead24 to negative line. For lowering, positive lead 29, by controller to lead,I 26, armature 18, lead' 25, safety switch blade 1, lead 28, b controller to lead 27 field winding 19 andA ead y24 to negative roo line. It is obvious that the position of 'the carrier 11 depends upon the position of the chain block. Assuming the chain block to have normal travel the carrier 11 will travel forward and backward between the end bearing 16 and the finger 9, the hoisting motion of the chain block actuates the carrier 11 toward the finger 9. When the chain block raises sufficiently high toassume the aforesaid' redetermined position the carrier 11 and ger 9 engage and a further hoisting of the chain block will cause the carrier 11 to actuatev and revolve finger 9 upon its pivot 10, and -thereby releasing the pin 8. The spring 5 then reacts, augmented by the spring 7 thereby causing a quick disengagement of switch blade l and clip 3. The reaction ofthe springs ard with such force as to cause the switch blade 1 to engage with the clip 4. It will be seen from Fig. 3 that only a lowering motion can be accomplished which will be substantially as follows, positive lead 29, by controller to lead 26, armature 18; lead 25, switch blade 1, lead 23, field winding 19 and lead 24 to negative line. In order to accomplish a hoisting motion the switch blade will have to rengage with the clip 3. If the chain block is not lowered from the aforesaid extreme hoisting position3 it will be impossible for the finger 9 to engage with the pin 8 due to therelative osition and engagement of carrier 11 and ger 9. It will be seen that after a lowering of the chain block has been accomplished the switch blade 1 can then be held into engagemerit with the clip 3.

The foregoing movements accomplish the hereinbefore mentioned object of our said invention.

Having thus described the nature and object of our said invention and what we claim as new and desire to secure by Letters Patent, are- `1. In a limit switch of the character described the combination of an insulated pinion and a screw keyed to same and bearings for said screw anda-carrier threaded and adapted to traverse the said screw and to engage with a hereinafter mentioned dog or finger, and aguide for the said carrier,'a switching mechanism mounted on a base over the said screw, a finger or dog passing 'through and pivoted von said base and adapted to hold said switching mechanism in normal position, and a spring provided to actuate said switching mechanism upon the disengagement of said dog-or finger with said switching mechanism, all substantially as and for the purpose shown and described. 2. In a limit switch of the character -described the combination of an insulated pinion and a screw keyed to same, and bearings for said screw and a carrier threaded and adapted to traverse the said-screw and also to engage with a hereinafter mentioned finger or dog upon a predetermined movesenses ment of said dog or finger, and a guide for said screw and passing through said carrier,

a sin le pole double throw switch mounted on a ase over the said screw and carrier, a finger extending through Aand pivoted on said base, a pin`on the blade of said switch and ada ted to engage with said finger or dog in t e normal position of said switch, and a spring opposing the` engagement of the switch blade with the normal switch clip, and actuating the said switch upon the disengagement of the said finger or dog with said pin, all substantially as and for the purpose shown and described.

3. In a limit switch of the character described, an insulated pinion actuated. by a gear in a train of gears, a screw secured to said pinion, bearings provided for said screw, a carrier actuated by said screw, a guide for said carrier andpassing through same,`a switching mechanism mounted on a base over said screw, and a finger or dog holding said switching mechanism in normal position and adapted to engage with the said carrier upon a predetermined movement of said carrier, all substantially as and for the purpose shown and described.

4. In a limit switch of the character described, an insulated pinion, said pinion meshing with. a train of gears of a hoisting motion, a screw provided with bearings, said screw keyed to sald insulated pinion, a carrier, said carrier threaded and adapted to traverse said screw, a guide for said carrier, a switching mechanism mounted on a base over the said carrier, a finger or dog eX- tending through and pivotedon said base and adapted to engage with said switching mechanism in its normal Lposition and also with said carrier upon aV predetermined 'movement' of same, and a spring opposing the engagement of said switching mechanism in its normal position, andfactuating the switching mechanism upon the disengagement of said finger with said switchin mechanism, all substantially as and for t e purpose shown andv described. f

5. In alimit switch of the character described, an insulated pinion actuated by a; gear m a train of hoisting gears, a screw secured to said pinion, bearings provided for saidscrew, a carrierthreaded and adapted4 to traverse the saidscrew,a guide for said carrier and passing through same, a switching mechanism mounted on a base over said screw, and a finger or dog pivoted at said Abase and holding said switching mechanismV in normal position, said finger or dog adapted to engage with said carrier upon a redetermmed movement of said carrier, al substantially as and for the purpose shown and described.

6. In a limit switch of the character del scribed, an insulated pinion, saidl pinion meshmg with a gear in a train of hoisting gears, a screw provided with bearings, said screw secured to said insulated pinion, a carrier, said carrier threaded and adapted to traverse the said screw, al guide parallel to said screw and passing through the upper portion of said carrier, a switching mechanism mounted on a base over said carrier, a

finger or dogextending through said base and pivoted ythereon and adapted to engage with said switching mechanism in its normal Vposition and also with said carrier upon a .v zo

predetermined movement of same, and a spring opposing the engagement of said switching mechanism in its normal position and actuating same upon the disengagement of said finger or dogrk with1said switching mechanism all substantially as and for the purpose shown and described.

7l In a limit switch of the character described, an insulated pinion, said pinion meshing with a gear in a train lof hoistingv gears, a screw provided Wlth bearings, said screw keyed to said linsulated pinion, a carrier, said carrier threaded and adapted to traverse the `said screw,4 a guide parallel to said screw and passing through the up er por ,tion of said carrier, a single pole doubfe throw switch mounted on a base over the said carrier, al inger extending through said base and adapted to engage with said switch and also upon a predetermined movement e of said carrier, and a springopposing the engagement p of the blade of the aforesaid switchwith the normal switch clip, and actuating the aforesaid switch upon-a disen agement of'said switch with said finger, all substantially as and for the purpose-shown and described.

8. In a limit switch of the character described, an insulated pinion', said pinion meshing with a gear in a train of hoisting gears, a screw provided with bearings, said screw keyed to said insulated pinion, a carrier, said carrier threaded and adapted to traverse the said screw, a guide parallel 4to said screw and passing through the upper portionof said carrier, a single pole double throw switch mounted onv` a base over the 'said carrier, a linger extending through said base, a pin on the blade of the aforesaid switch and adapted to enga -e with the aforesaid finger upon the norma position of said switch, and also en aging with the aforesaid carrier upon a pre etermined movement of said carrier, and a spring opposing the engagement of the switch blade with the normal switch clip, and actuating the aforesaid switch' upon the disengagement of the afore- 

